Increase the page space growth rate when there is insufficient free space.

runtime/vm/pages.h

Index: runtime/vm/pages.h
diff --git a/runtime/vm/pages.h b/runtime/vm/pages.h
index 7022a78d3f23f76da4f51898a82599b01f9f8ed0..a182ab35a6e07c35f2c52ebdc7eb62647c5dec6f 100644
--- a/runtime/vm/pages.h
+++ b/runtime/vm/pages.h
@@ -118,7 +118,7 @@ class PageSpaceController {
   // heap_growth_ratio % of memory got deallocated by the garbage collector.
   // In this case garbage collection will be performed next time. Otherwise
   // the heap will grow.
-  void EvaluateGarbageCollection(size_t in_use_before, size_t in_use_after,
+  void EvaluateGarbageCollection(intptr_t in_use_before, intptr_t in_use_after,
                                  int64_t start, int64_t end);
 
   void Enable() {
@@ -135,6 +135,10 @@ class PageSpaceController {
   // memory, then the heap is grown. Otherwise garbage collection is performed.
   int heap_growth_ratio_;
 
+  // The desired percent of heap in-use after a garbage collection.
+  // Equivalent to \frac{100-heap_growth_ratio_}{100}.
+  double desired_utilization_;
+
   // Number of pages we grow.
   int heap_growth_rate_;